This invention relates to electronic devices and more particularly, to portable electronic devices with satellite navigation system capabilities.
Electronic devices use satellite navigation systems to support navigation functions. For example, an electronic device may use a satellite navigation system such as the Global Positioning System (GPS) to obtain position information, timing information, and other navigation information. The Global Positioning System includes satellites that orbit the Earth, Earth-based control and monitoring stations, and GPS receivers that are located within the electronic devices. GPS services may be provided on a continuous basis anywhere that is within range of the orbiting satellites.
A portable electronic device may include a GPS receiver. The GPS receiver is used to determine the current position (location) of the portable electronic device. During operation, the GPS receiver may receive data streams from GPS satellites orbiting the Earth. Using a local clock, the GPS unit analyzes each data stream to make a transit time and distance estimation.
A method known as geometric trilateration may be used to determine the location of the electronic device by analyzing the estimated distances of each of the satellites relative to the GPS receiver. It may be desirable to characterize the performance of the GPS receiver to determine whether the GPS receiver satisfies design criteria during normal wireless operation.
Conventional arrangements for testing GPS receiver performance involve placing an electronic device under test (DUT) within a test chamber and using a single test antenna within the test chamber to transmit GPS signals to the GPS receiver. The test antenna transmits the GPS signals at a selected power level. If the signal strength of GPS signals being received at the GPS receiver exceeds a predetermined threshold level, the GPS receiver satisfies design criteria. If the signal strength of the GPS signals being received at the GPS receiver is less than the predetermined threshold level, the GPS receiver fails to satisfy design criteria. Testing GPS performance using only one antenna, however, does not accurately characterize the behavior of the GPS receiver in a real world environment (i.e., a real world environment in which multiple GPS satellites simultaneously transmit radio-frequency signals to the GPS receiver).
It would therefore be desirable to be able to provide improved ways for testing satellite navigation system receiver performance.